Field of the Invention
The present invention relates to a touch sensing system.
Discussion of the Related Art
User interface (UI) is configured so that users are able to communicate with various electronic devices and thus can easily and comfortably control the electronic devices as they desire. Examples of the user interface include a keypad, a keyboard, a mouse, an on-screen display (OSD), and a remote controller having an infrared communication function or a radio frequency (RF) communication function. User interface technology has continuously expanded to increase user's sensibility and handling convenience. The user interface has been developed to include touch UI, voice recognition UI, 3D UI, etc. Gesture UI for sensing user's gestures has been recently applied to household appliances.
The touch UI senses an object which directly contacts a touch screen or approaches at a height close to the touch screen. The touch UI senses a user' touch input or an object's touch input using the touch screen including resistive touch sensors or capacitive touch sensors.
The touch screen may be implemented by capacitive sensing technology. The capacitive sensing technology senses changes in capacitances by a touch or a proximity of a conductive object due to a coupling effect of capacitances using capacitive sensors. The capacitive sensors are classified into mutual capacitive sensors and self capacitive sensors. The mutual capacitive sensor is formed at a crossing of two lines, which are perpendicular to each other with a dielectric layer interposed therebetween. As shown in FIG. 1, the self capacitive sensors are as many as segment electrodes C1 to Cn respectively connected to lines 10 and are formed on a touch screen. FIG. 1 shows a portion of the lines 10 connected to the self capacitive sensors. In FIG. 1, “DIC” is a display driving integrated circuit (IC) attached to a substrate of a display panel 100. The display driving IC DIC is connected to data lines and gate lines (or scan lines) formed on a pixel array of the display panel 100 and applies data to pixels.
If the m×n self capacitive sensors are arranged on the touch screen, the m×n lines 10 are necessary to individually apply a driving signal to the segment electrodes C1 to Cn. The lines 10 are connected to terminals of a touch detection IC through a flexible print circuit (FPC). A pad 11 connected to one end of each line 10 is connected to an output terminal of the FPC, and the other ends of the lines 10 are respectively connected to segment electrodes C1 to Cn. As the number of lines 10 increases, the number of output terminals of the FPC increases. Therefore, the size of the FPC increases, and the number of terminals of the touch detection IC increases.
The number of lines may be reduced to (m*n)/x using a 1-to-x multiplexer (or MUX). Further, a sensing time may be increased by dividing the capacitive sensors into a plurality of groups and simultaneously sensing the capacitive sensors belonging to each group. However, even if the above-described methods are applied, the number of lines required in the self capacitive sensors is more than the number of lines required in the mutual capacitive sensors. Because of this, when the touch screen is implemented using the self capacitive sensors, it is difficult to increase the number of segment electrodes. Hence, it is difficult to increase the size and a resolution of the touch screen.